Various wireless access technologies have been proposed or implemented to enable mobile stations to perform communications with other mobile stations or with wired terminals coupled to wired networks. Examples of wireless access technologies include GSM (Global System for Mobile communications) and UMTS (Universal Mobile Telecommunications System) technologies, defined by the Third Generation Partnership Project (3GPP); and CDMA 2000 (Code Division Multiple Access 2000) technologies, defined by 3GPP2.
As part of the continuing evolution of wireless access technologies to improve spectral efficiency, to improve services, to lower costs, and so forth, new standards have been proposed. One such new standard is the Long Term Evolution (LTE) standard from 3GPP, which seeks to enhance the UMTS wireless network.
Dual-mode mobile stations can perform access using different types of wireless access networks, such as a legacy HRPD (High Rate Packet Data) wireless access network (as defined by CDMA 2000) or a E-UTRAN (Evolved UMTS Terrestrial Radio Access Network, as defined by 3GPP). The E-UTRAN wireless access network allows for access of 4G (fourth generation) wireless services, such as those provided by LTE.
As service operators evolve from legacy wireless access networks to 4G networks, such service operators typically have to support subscriber access at both types of networks. When a mobile station (such as a dual mode mobile station) attaches to an E-UTRAN wireless access network, for example, services provided in the legacy network may no longer be available to the mobile station.